Older adults are living longer, in part due to advances in medical science, public health initiatives, and global economic growth. However, the reality of an extended life expectancy for the majority of Americans includes living with multiple chronic conditions as they age (National Institute of Aging, 2016). Further, chronic illnesses make up seven out of the ten leading causes of death, so most will die from one of those conditions (Kochanek, Murphy, Xu, & Arias, 2019). Though nomenclature has changed over time, the terminal phase of chronic illness has more recently been called serious illness (Kelley, 2014). Serious illness impacts life expectancy, function, and overall well-being (Kelley, 2014). Understanding the resources that people use to respond to, process, and move forward with serious illness is key in targeting nursing-directed care for this population. Inner strength encompasses 'an internal developmental capacity that supports positive movement through challenging life events' and has implications for quality of life (Smith, Dingley, & Roux, 2019, p. 38). Older adults living with serious illness may use inner strength as a resource. However, previous conceptual and theoretical models of inner strength are limited in their applicability to people in the terminal phase of a chronic illness. A refined understanding of the nature of inner strength is imperative for informing nursing care that addresses the needs of people who face ageing with serious illness.